About one in nine adults past 45 say their memory is slipping. A name won't come at dinner. Then a task falls off the list. You walk into a room and stand there, sure you came in for something.

Maybe you've tried puzzles, or a bottle of pills from the drug store. Some of it helps a bit. Most of it costs more than it gives back...

But there is a plant in the produce aisle with a very old claim on memory. It costs a few dollars a bunch. And a lab in the north of England took that old claim and put it to a real test.

Let me explain...

The story goes that Greek students tucked rosemary in their hair while they read. They hoped the sharp smell would help the words stick. No one can say for sure how true that tale is. But the link between this herb and the mind is very old.

Its Latin name tells you where it grew. Ros marinusmeans "dew of the sea." Wild rosemary clung to dry, rocky hills on the Mediterranean coast. Later, English ears heard "rose" and "Mary" in the name, and the spelling bent to match.

Around the year 800, Emperor Charlemagne sent out a list of plants to be grown on his royal farms. Rosemary made the list. Eight hundred years after that, Shakespeare gave Ophelia the line most of us still know: "There's rosemary, that's for remembrance."

So the claim held for a very long time. But a claim is not proof. Could a whiff of this herb do much of anything at all?

They scanned 12,000 people and found something terrifying:

Everyone with vision loss had clogged micro-vessels in their eyes.

Not just an eye problem. A whole-body problem.

The same blockages dimming your sight are cutting oxygen to your heart.

Hazy vision lately? That's your warning about cardiac risk.

Most doctors never make this connection.

Oxford researchers did. Then found a red root technique that clears the blockages.

→ Watch the 2-minute explanation

Vision restores. Heart protected. Some see results in 48 hours.

Rosemary's smell comes from a few light oils in the leaf. The main one is a compound called cineole. It's the same sharp note you smell in a cough drop.

These oils don't stay put. They lift off the leaf and float in the air. When you breathe them in, some pass through the thin lining of your nose and lungs and into your blood.

That part is not a guess. A team at Northumbria University in Newcastle checked it with a needle.

Mark Moss and Lorraine Oliver sat 20 adults in a small booth with rosemary oil in the air. Some sat for four minutes. Others sat for ten. Then each one took tests of mental math and quick visual checks. After that, the team drew blood.

The cineole was there, in the blood. And the more of it each person had, the faster and more correct their answers were. The team published the work in 2012.

What the compound does once it gets to the brain is still an open question. Lab work hints at a few paths. None of them is settled in people. So for now, the plain finding is the one worth holding: breathe it in, and it shows up in you.

Northumbria University, 2016: In a room with rosemary oil in the air, adults 65 and older scored 15% higher on tests of remembering to do things later.

Four years later, the same lab ran a larger trial. This time, every person was 65 or older. There were 150 of them.

Each one was sent at random to one of three rooms. One had rosemary oil in the air. A second had lavender. The third had no smell at all.

Lauren Bussey and Mark Moss tested a kind of memory you use every day without a name for it. It's the kind that tells you to take a pill at noon, or to pass on a message when you see a friend. Researchers call it "prospective memory." You can think of it as remembering to remember.

The rosemary group did best. Lavender made people feel calm, but it didn't help their scores. The team shared the results at a meeting of the British Psychological Society in 2016.

Now the honest part, and it matters.

Both studies used rosemary oil in a fan, not a sprig in a hand. A crushed leaf at your counter gives off far less. No one has tested the sprig. So the home version below is a cheap, safe try, not a proven dose.

The first study was small, just 20 people. It found a link between blood levels and scores, which is not the same as proof that one caused the other. The second was a talk at a meeting, not a paper checked by other experts. And neither one looked at memory over months or years.

That's a short trail. It points the right way. But it does not reach the end.

Rosemary sits in the mint family, next to basil, thyme, oregano and lavender. In 2017, plant experts moved it into the sage group, so its new formal name starts with the word for sage.

Sage has its own small pile of memory work. Many herbs in this family share the same kinds of light oils. That may be part of why so many old herb lists tie them to a clear head.

Rosemary still grows wild on the dry coast where it started. Thin soil. Salt air. Dew of the sea, just as the old name said.

Fresh rosemary should be deep green and soft enough to flex. If the stem snaps and the needles rain down, it has been sitting a long time. Rub one leaf and smell your thumb. Strong and piney is what you want.

Roll the sprigs loosely in a slightly damp paper towel and slip them into a bag in the fridge. North Dakota State University's extension service says fresh rosemary keeps 10 to 14 days this way. You can also freeze whole sprigs and strip the leaves straight from frozen.

Dried rosemary still cooks well, but it won't give you much smell when you rub it. The same extension service says the leaves from three fresh sprigs equal about one teaspoon of dried. Use fresh when you want the scent.

Those Greek students had a green sprig and a hunch. Shakespeare had a good line. Nobody drew their blood.

Two thousand years later, Mark Moss and his team did. The compound got into the blood, and the scores leaned the right way. It's a small start, not a cure, and the herb at your store was never in the trial.

But it costs little, it smells good, and it makes dinner better either way. Pick up a bunch this week. Keep a sprig close. And let the smell remind you of the thing you came in the room to do.